On Fri, Jun 09, 2023 at 09:37:56AM +0200, Ahmad Fatoum wrote: > On 09.06.23 09:29, Sascha Hauer wrote: > > On Thu, Jun 08, 2023 at 09:24:18AM +0200, Ahmad Fatoum wrote: > >> Best practice is for each board to populate $global.system.partitions > >> or $global.fastboot.partitions with a string exporting its flashable > >> devices in a descriptive manner, e.g. "/dev/mmc0(eMMC),/dev/mmc1(SD)". > >> > >> This often goes into BSPs though, so upstream boards are left without > >> default partitions, making use a bit cumbersome. Make this easier > >> by providing three new magic specifiers: > >> > >> - nvmem: exports all registered NVMEM devices (e.g. EEPROMs, Fuse banks) > >> - block: exports all registered block devices (e.g. eMMC and SD) > >> - auto: currently equivalent to "nvmem,block". May be extended > >> to raw MTD and UBI in future > >> > >> This makes it easy to export devices on any board: > >> > >> usbgadget -A auto -b > >> > >> or > >> > >> usbgadget -S auto,/tmp/fitimage(fitimage)c > >> > >> Signed-off-by: Ahmad Fatoum <a.fatoum@xxxxxxxxxxxxxx> > >> --- > >> Documentation/user/usb.rst | 17 +++++++++++++++++ > >> common/block.c | 16 ++++++++++++++++ > >> common/file-list.c | 29 +++++++++++++++++++++++++++-- > >> drivers/nvmem/core.c | 16 ++++++++++++++++ > >> include/block.h | 6 ++++++ > >> include/linux/nvmem-consumer.h | 8 ++++++++ > >> 6 files changed, 90 insertions(+), 2 deletions(-) > >> > >> diff --git a/Documentation/user/usb.rst b/Documentation/user/usb.rst > >> index f2f57ead98d4..6fed0f619b32 100644 > >> --- a/Documentation/user/usb.rst > >> +++ b/Documentation/user/usb.rst > >> @@ -73,6 +73,23 @@ Example: > >> > >> /dev/nand0.barebox.bb(barebox)sr,/kernel(kernel)rc > >> > >> +Board code authors are encouraged to provide a default environment containing > >> +partitions with descriptive names. For boards where this is not specified, > >> +there exist a number of **partition** specifiers for automatically generating entries: > >> + > >> +* ``nvmem`` exports all registered NVMEM devices (e.g. EEPROMs, Fuse banks) > > > > Blindly exporting NVMEM devices is not a good idea. As the description > > says it's used for fuse banks. These are write-once and modifying them > > is potentially dangerous. Also it's fastboot which means you can't even > > read them before modifying them and there is no way to only partially > > write them. > > > > There might be good reasons to export some specific NVMEM device, but > > then this should be explicitly exported and not by default. > > The few fuse bank drivers that can actually blow fuses have a device > variable that needs to be written to unlock write access. > > But yes, the inability to write them partially makes the write > useless. I will just resend without nvmem. Side note: the fastboot protocol would even allow to do partial writes, but I don't think there's a way to make use of them with the fastboot tool. Sascha -- Pengutronix e.K. | | Steuerwalder Str. 21 | http://www.pengutronix.de/ | 31137 Hildesheim, Germany | Phone: +49-5121-206917-0 | Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
